The permanent magnet motor will demagnetize when the temperature exceeds 200 degrees Celsius

The permanent magnet motor will demagnetize when the temperature exceeds 200 degrees Celsius

I have introduced in the previous issues of the column, permanent magnet synchronous motor is currently a relatively efficient solution in the motor. However, permanent magnets have a fatal flaw, which is demagnetization when working at high temperatures for a long time. Once demagnetized, motor power and efficiency are greatly attenuated. This is a very important bottleneck restricting the development of hub motors. Because once the motor is placed in the hub, it will be located very close to the brake disc. The high temperature of the vehicle due to braking is directly transmitted to the motor, and the risk of demagnetization occurs as soon as the motor heats up.

At present, several suppliers around the world who are committed to research and development of wheel motors, such as Michelin and Bridgestone, are designing water cooling systems to dissipate heat from the motor. On the one hand, the stator of the motor is cooled by a water-cooling system, and on the other hand, the braking system is reduced as much as possible by an efficient braking kinetic energy recovery system, thereby reducing the braking load. Finally, due to the temperature generated by the brakes, the heat is dissipated through a good ventilation and heat dissipation design, and a silicon steel sheet is added between the brake system and the motor to insulate, thereby controlling the limit temperature of the battery to below 140 degrees. With the above solution, the current temperature of the hub motor can be controlled to less than 100 degrees Celsius under extreme braking conditions. Therefore, even the case of high temperature demagnetization is being overcome by suppliers. I believe that in the near future, the quality of the sprung mass such as SUV or hard cross-country will be large, and the electric vehicle with less dynamic control will take the lead in mass production of the hub motor. Such a solution results in longer cruising range and a more economical car experience.